The present invention relates to the tip of an ultrasonic endoscope, which is to be inserted into a body cavity to perform ultrasonic scan and optical viewing simultaneously.
The tip of the insertion portion of an ultrasonic endoscope is equipped with an ultrasonic wave transmitting/receiving member and an optical viewing member. An instrument-inserting channel is also provided in the tip of the insertion portion of the ultrasonic endoscope so that an instrument such as one for injecting a liquid into the body can be passed through the instrument-inserting channel. Because of this structural complexity, the tip of the insertion portion of the ultrasonic endoscope is inevitably bulky and causes greater pain to the patient under examination than in the case of ordinary endoscopes.
An instrument projects from the tip of the insertion portion of an ultrasonic endoscope in various directions depending upon its design specifications. A forward projecting layout is recommended from the viewpoint of space economy, making the tip of the insertion portion the most compact in size.
A typical forward projecting layout is described in Unexamined Published Japanese Patent Application (kokai) No. 265535/1990, and it is characterized in that both the exit opening of the instrument-inserting channel and the viewing window are provided at the end face of the tip of the insertion portion of an ultrasonic endoscope and that an ultrasonic oscillator array for radial scan is provided annularly around the tip of the insertion portion.
However, if the viewing window is provided at the end face of the tip of the insertion portion and the ultrasonic oscillator array annularly around the tip of the insertion portion, the direction of ultrasonic scan is out of the visual field of optical viewing. Therefore, the site under ultrasonic scan cannot be viewed optically at the same time, making it impossible to perform reliable examination smoothly.